Can an Attacker Reverse a Hashed Password If They Have Access to the Salt?

Improving Password Hashing with Random Salt

Question:

While using a hashed password method (sha512(password.salt)) seems more secure than a simple MD5 hash, some concerns arise:

• The salt value is stored alongside the hashed password.
• If an attacker gains access to both the hash and salt, wouldn't they be able to reverse the hash?

Answer:

Despite the attacker's potential access to the salt, the security of the password hashing method remains intact.

Purpose of Salt:

The salt adds entropy to the hash, making brute-force attacks more challenging. Without salt, an attacker can use pre-computed "rainbow tables" to quickly and easily obtain the plaintext password from the hash.

Defense Against Brute Force Attacks:

By introducing a unique, random salt for each password, it becomes impractical for attackers to create rainbow tables due to the overwhelming number of possibilities. This increases the computational time and resources required for a successful brute-force attack.

Overcoming Concerns:

• Even if the attacker obtains both the hash and salt, they still face the difficulty of cracking the hash due to its high entropy resulting from the random salt.
• To further enhance security, consider implementing additional techniques such as repeated hashing or key derivation functions like PBKDF2.

Mandatory Protection:

In today's computing landscape, employing these password hashing mechanisms is crucial. The availability of powerful cloud-based resources makes brute-force attacks more feasible and necessitates robust security measures to protect user passwords effectively.

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